Possible regression in Fedora 44: no audio from my monitor over usb-C but it plays through HDMI

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1

I have a laptop (Thinkpad X1 Extreme Gen 2 - it has an Nvidia card) and a monitor (Dell UltraSharp43 - U4320Q). I connect the monitor to the laptop via USB-C. The system sees the monitor, I can select it via KDE’s applet or I can send audio to it via aplay like this, but without producing any sound:

aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: CX11880 Analog [CX11880 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 3: HDMI 0 [DELL U4320Q]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 7: HDMI 1 [DELL U2717D]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 9: HDMI 3 [HDMI 3]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

#plays nothing
aplay -D plughw:1,3 /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono

# plays sound through laptop's speakers
aplay -D plughw:0,0 /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono

I tried restarting wireplumber and pipewire and removing any audio configuration I had in my home folder. This used to work perfectly in Fedora 43. Curiously, when I connect the monitor through an actual HDMI cable, the audio works. I am running out of ideas, it sounds like some regression in how HDMI over USB-C works. Before filling a bug, has anybody any ideas what else might be wrong (and what logs can I provide with the bug report)?

2

Actually, I booted up both Fedora Live 44 and 43 and audio over USB-C does not work in either of them (it works over HDMI). Which is super weird. So it seems it cannot be a software problem, as it used to work with Fedora 43, but what kind of hardware problem would this be? Should I try different USB-C to USB-C cable? I tried reseting the monitor to factory settings and unplugging it for a few minutes, neither of which helped. I am utterly confused.

3

The kernel driver nouveau does not support audio output via DP.

You need to install the nvidia driver.

4

Aha, good catch. I did not realize I was running nouvou drivers at all, or maybe that nvidia drives was not running properly (nvidia was installed and nouveau now works so well I did not realize I was not running nvidia).

Actually, a problem seems to be that the appropriate modules (?) were not compiled (?) with sudo akmods --force - I was getting an error saying

Could not find files needed to compile modules for /boot/efi//3df672eef9054350b62cccb2eae56a38/7.0.1
2-201.fc44.x86_64/linux
Are the development files for kernel /boot/efi//3df672eef9054350b62cccb2eae56a38/7.0.12-201.fc44.x86
_64/linux or the appropriate kernel-devel package installed?

The magic comnmand was sudo akmds --force --kernels 7.0.12-201.fc44.x86_64

I am running sdboot, installed from netinstall - it seems this might be what is confusing akmods. I am up until now not sure if the proper path for that is /boot/efi/ or /efi` - the documentation for sdboot on Fedora is not exactly stellar, or I have not found the proper one :-/.

I also downgraded to driver version 580 based on this: NVIDIA Drivers Not Working On Fedora 44 - #19 by diaxen

I will not try the new drivers, I suspect the problem was the broken akmod.

By the way, in the middle of fiddling with the drivers, all graphical output to the external monitor was not working. As I was running the akmod command successfuly, the image appeared all of a sudden.

But anyway, the sound through the monitor now works.

Edit: version of the driver was not the culprit, it now works with version 595 too.